Water hardness in Patterson
22.7 gpg very hard
Tap water in Patterson is very hard: 22.7 gpg (389 mg/L · 21.8 °dH · 38.9 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA5010017 (2026-06) · data checked 2026-10-19
Range across supply zones: 324–464 mg/L.
The Patterson figure comes from State Water Resources Control Board lab results for the City of Patterson system. The median of 13 results from 2022 to 2026, taken at 8 well points, is 389 mg/L as CaCO3 (22.7 gpg), with a range of 323.6 to 464.2 mg/L. This is among the hardest water in our US set. Scale builds very fast, and a softener is worth serious consideration.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 22.7 gpg |
|---|---|
| Utility | Patterson, City Of |
How Patterson compares
- Tap water in Patterson is 151 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 68 of 1372 in the United States (1 = hardest); 95 % of these cities have softer water.
- In California it is number 19 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Ceres, 21 km away (2.8 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Patterson
| Brand | Setting for this water |
|---|---|
| Bosch | H06 |
| Miele | 22 °dH |
| AEG / Electrolux | 5 |
| Beko | 6th |
| Hoover | S3 |
| LG | H4 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Patterson water hard or soft?
It is very hard: 389 mg/L as CaCO₃ (22.7 gpg, 21.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Patterson safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is Patterson water?
22.7 gpg, equal to 21.8 °dH, 38.9 °fH or 389 mg/L calcium carbonate.
What dishwasher salt setting should I use in Patterson?
For 389 mg/L (21.8 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Patterson?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA5010017 (2026-06). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA5010017 · Outdated figure? Tell us